Changes of normal coordinates and geometrical parameters of a molecule in a laser field

General formulas are derived that describe the changes in equilibrium distances, valence angles, and vibrational frequencies of a polyatomic molecule in a strong laser field. It is shown that the coordinates of normal vibrations do not change in the second order in the field strength. For a nonlinear triatomic molecule of the type of $A_2B$, the changes of geometrical characteristics and vibrational frequencies are obtained in an explicit form.